THE LIVING SUBSTANCE 



sistency, type and abundance of inclusions, and reactions to 

 chemicals. Facts gained from a knowledge of these and similar 

 properties give us all the insight we have into the structure of 

 protoplasm and the mechanism of protoplasmic behavior. 



"St 







Fig. 2.— a small portion of the protoplasm of a myxomycete (at higher magni- 

 fication than in Fig. 1). The largest oil globules (of 10 m diameter) appear as 

 bright spots. (The two or three large circular areas are openings in the 

 Plasmodium.) The channels of flow are broad bands of darker color. (From 

 J. Comandon.) 



Protoplasm (Fig. 1) is a translucent, grajdsh, and slimy sub- 

 stance, usually capable of flowing freely, though often of moder- 

 ately high consistency even when flowing. It looks much like 

 the white of an egg though less homogeneous, as only rarely is it 

 devoid of visible inclusions. 

 Under low magnification, proto- 

 plasm appears to be a dispersion 

 of many globules and tiny granules 

 in a thick matrix. The granules v>'v_x^y 

 are often mere specks when seen r^Qw^ 

 under the highest magnification of 

 the microscope. It is impossible 

 always to say whether proto- ^^''- 3.— Sketch of the protoplasm 



. . ^ 01 an ilichinoderm egg. 



piasmic particles are actually 



granules or droplets (i.e., whether of solid or liquid material). 

 The distribution of granules and globules is usually a heterogene- 

 ous one, as in the Plasmodium of a myxomycete (slime mold) (Fig. 

 2), but it may assume a certain degree of symmetry, as in 

 echinoderm (e.g., starfish) eggs (Fig. 3). Great care must be 



